I would think etiquette is limited to hypothetical imperatives, insofar as the formulation of these satisfies a subjective want, contingent on how it makes the subject feel because of the action he takes.
But that is not and never was the object of moral philosophy proper, in that the actions of a group is always conditioned by the actions of individuals in it, which makes explicit the distinction in ethical behavior of the subject in juxtaposition to his fellows, and the moral volition of the subject himself without any regard for anything other than his own rational disposition, whatever it may be.
Foot is right enough in supposing the construction of a philosophy predicated on hypothetical imperatives, but to describe it as a possible moral philosophy methinks ‘tis a bridge too far.
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Foot: “….The desires on which a hypothetical imperative is dependent may be those of one man, or may be taken for granted as belonging to a number of people, engaged in some common project or sharing common aims….”
Insofar as this is true enough, it presupposes that which is possibly common to every man, and simultaneously inquires as to what form that commonality can possibly have, not across cultures and communities, but across ages.
So historical precedent informs that as yet not every human will ever agree on any one particular thing, so if there is a manifest commonality in humans in general, it must be in the form of a preferred condition each and every one of them desires for himself. And if such apodeitic commonality is conceivable, then the deduction of a moral necessity follows from it as a matter of course.
Now the fun part: any one can perform an act he himself considers to be a good act, but feel no pleasure for having done it. That very same person, at necessarily a different time, can feel altogether comfortable with himself having performed an act he already knows is not good.
If every single human ever is subject to this rational dichotomy, what possible commonality can there be for them all. It is clear happiness itself is not sufficient to satisfy the requirement, for it is proved a subject in his moral action is not necessarily happy for it.
Kant set the stage for pure moral philosophy with the notion that failing the effects of happiness in and of itself, it may be then the worthiness for being happy, which satisfies the criterion of that for which every human seeks for himself, and it is the categorical imperative alone, in its “shall” relation to moral interests, by which the worthiness for being happy is determinable.
That poor schmuck feeling down for having done something he knows is painful for somebody else, still can consider himself a properly moral subject for having conformed to his own moral principle.